Polyps are defined as growths or masses protruding from a mucous membrane of the body. Polyps may be classified by their morphology. A polyp may be attached to a mucous membrane by a stalk (pedunculated polyp) or the polyp may have a broad base (sessile polyp). They may occur in the mucous membrane of many different types of organs, such as the nose, mouth, stomach, intestines, rectum, urinary bladder, and uterus. Most polyps are benign and eventually stop growing, but some, may ultimately become cancerous tumors.
The probability of any single polyp becoming cancerous depends on its gross appearance, histological features, and size. Polyps greater than 1 centimeter have a greater risk of being or becoming cancerous than polyps smaller than 1 centimeter. As these tumors grow larger, they can invade the underlying tissue layers supporting the polyp. In the final stages, the cancer may metastasize to other distant organs. Particularly common, yet readily treatable, are polyps of the colon. Colorectal or gastric cancers, often beginning as benign or precancerous polyps, can essentially be avoided if detected and treated in their early stages by performing a polypectomy.
Polypectomy is the medical term for removing polyps, particularly small polyps of the colon and stomach. These can be removed by using a biopsy forceps, which removes small pieces of tissue. Larger polyps are usually removed by putting a noose, or snare, around the polyp base or stalk and burning through the tissue with an electric instrument (cauterization). Other devices employ physical or electrical scraping of the lining of an organ, such as the colon, rectum or stomach, to remove a polyp.
In almost all cases, the severed polyps are retrieved for examination by a pathologist. For decisively ruling out cancer, a sample of adequate size is required for the pathology laboratory. This includes a clean margin around the polyp as well as all the layers of the organ wall.
Complications, however, sometimes occur during polypectomies. Electrocauterization, for example, often produces desiccation and perforation of the organ wall. Other complications include non-specific tissue destruction caused by unnecessary heating in the treatment environment resulting from the presence of saline, a highly conductive electrolyte. Finally, conventional electrosurgical cutting or resecting devices tend to leave the operating field cluttered with tissue fragments that have been resected from the target tissue. These tissue fragments make observation of the surgical site extremely difficult.
An endoscopist's ability to resect large sessile polyps is limited, due to the inherent limitations of endoscopes, the lack of polyp accessibility, the lack of available accessories, and the difficulty in achieving full thickness resection. While colonoscopes/gastroscopes are widely used for diagnostic purposes their therapeutic abilities are limited. This is a result of the need to control and manipulate instruments, including the endoscope's distal end, from outside the body. Because of the limitations in current technology, large polyps that cannot be resected endoscopically, or polyps suspected to be malignant, are referred to surgery.
Prior art snare instruments used in polypectomies have several problems. First, it is difficult for the physician to precisely position the snare. Typically, it is necessary for the physician to repeatedly push, pull, and torque the sheath and the shaft of the instrument in order to position the snare around the polyp. Second, prior art instruments are not capable of efficient steering, because the shaft generally used includes a cable having low torsional stiffness. Third, while several attempts have been made at providing a snare instrument with a handle adapted to more adeptly steer the snare, most such prior art instruments do not specifically allow for rotating the snare so as to position it relative to the polyp. Rather, the physician must rotate the shaft of the instrument by tightly gripping and rotating the sheath where it enters the endoscope in an effort to try to maneuver the snare over the polyp.
Mechanical surgical clips for use in endoscopic surgery are known; however, they too have drawbacks. The typical known clip is a two legged clip that is passed through an endoscope's working channel via a flexible delivery catheter. Because the clip needs to pass through the endoscope, the clip's size is limited. Size limitations prevent the clip from being able to clamp off all of the vessels in the tissue around a wound. Additionally, the clip is unable to provide sufficient clamping force because of its structural design. An additional problem with these clips is that when delivering these clips to the wound site, good visualization of a bleeding vessel cannot be obtained. The endoscopist may be required to blindly attach the clip, resulting in an imprecisely performed procedure that requires guess work on the part of the endoscopist.
Currently, there are two endoscopic techniques used to resect large polyps. However, these are complicated, require significant experience and instrumentation, may be associated with complications and require repeated procedures to achieve complete resection. Determining the pathology of the lesion is usually limited because of the endoscopists' inability to perform a full thickness resection. In one technique, the piecemeal technique, a snare is used to remove the polyp piece by piece. In many cases this procedure needs more than one session to completely resect the polyp. The samples sent for pathology using this technique have the following drawbacks: loss of orientation of the resected tissue (polyp), inability to identify infiltration beyond the mucosa to diagnose malignant changes, inability to conclusively comment on the margins of resection, and inability to judge completeness of the resection. This leads to frequent follow-up endoscopic surveillance, adding to patient discomfort and extra costs to the health care system.
The second and more advanced technique is mucosectomy. With this technique the polyp is first elevated from the submucosa using a submucosal injection of a variety of solutions. The polyp is then excised using a variety of knives and/or snares. This procedure requires experience with advanced endoscopic techniques and may be associated with serious complications such as bleeding and perforation, complications that may result in surgery and hospitalization. A prerequisite for a safe mucosectomy is that the polyp should not invade the submucosa. Evaluation by high frequency intra-luminal endosonography is mandatory prior to performing a mucosectomy, a procedure available at only a limited number of endoscopy centers throughout the world. Although lateral margins can be commented upon in a specimen obtained through mucosectomy, evaluation of the deeper margin of the specimen may still be in adequate.
An optimal solution would involve the resection of the entire polyp together with adequate margins (i.e. surrounding normal tissue) and the various layers of the polyp's adjacent organ wall, mucosa, submucosa, muscular propria layer and serosa (Full Thickness Resection). The tissue deficit should be endoscopically closed at the same time. To date, the only full thickness resection systems, sub-systems and methods discussed in the patent literature employ surgical staples. Staples often lead to undesired complications such as leakage of blood and other body liquids into the region of the resected polyp, particularly polyps of the colon, often resulting in severe infection. Other complications include strictures and inflammatory reactions to the foreign bodies left behind.
An additional problem with staple systems and methods is that they require a stapling mechanism which generally is relatively large and fairly rigid. This limits the maneuverability of an endoscope and does not allow approach to all locations.
Therefore, there remains a need for a method, a system and elements of a system which would facilitate full thickness resection without the drawbacks discussed above.